Support for Docker "--volume" mounts during integration tests.

libcnb-test/src/container_config.rs

@@ -31,6 +31,7 @@ pub struct ContainerConfig {
     pub(crate) command: Option<Vec<String>>,
     pub(crate) env: HashMap<String, String>,
     pub(crate) exposed_ports: HashSet<u16>,
+    pub(crate) volumes: Option<Vec<String>>,
 }
 
 impl ContainerConfig {
@@ -198,4 +199,31 @@ impl ContainerConfig {
 
         self
     }
+
+    /// Attaches container volumes. Useful for integration tests that
+    /// depend on persistent storage shared between container executions.
+    ///
+    /// See: [Docker CLI, Mount Volume](https://docs.docker.com/reference/cli/docker/container/run/#volume)
+    ///
+    /// # Example
+    /// ```no_run
+    /// use libcnb_test::{BuildConfig, ContainerConfig, TestRunner};
+    ///
+    /// TestRunner::default().build(
+    ///     BuildConfig::new("heroku/builder:22", "tests/fixtures/app"),
+    ///     |context| {
+    ///         // ...
+    ///         context.start_container(
+    ///             ContainerConfig::new().volumes(["/shared/cache:/workspace/cache"]),
+    ///             |container| {
+    ///                 // ...
+    ///             },
+    ///         );
+    ///     },
+    /// );
+    /// ```
+    pub fn volumes<I: IntoIterator<Item = S>, S: Into<String>>(&mut self, volumes: I) -> &mut Self {
+        self.volumes = Some(volumes.into_iter().map(S::into).collect());
+        self
+    }
 }

libcnb-test/src/docker.rs

@@ -13,6 +13,7 @@ pub(crate) struct DockerRunCommand {
     image_name: String,
     platform: Option<String>,
     remove: bool,
+    volumes: Option<Vec<String>>,
 }
 
 impl DockerRunCommand {
@@ -27,6 +28,7 @@ impl DockerRunCommand {
             image_name: image_name.into(),
             platform: None,
             remove: false,
+            volumes: None,
         }
     }
 
@@ -67,6 +69,14 @@ impl DockerRunCommand {
         self.remove = remove;
         self
     }
+
+    pub(crate) fn volumes<I: IntoIterator<Item = S>, S: Into<String>>(
+        &mut self,
+        volumes: I,
+    ) -> &mut Self {
+        self.volumes = Some(volumes.into_iter().map(S::into).collect());
+        self
+    }
 }
 
 impl From<DockerRunCommand> for Command {
@@ -98,6 +108,12 @@ impl From<DockerRunCommand> for Command {
             command.args(["--publish", &format!("127.0.0.1::{port}")]);
         }
 
+        if let Some(container_volumes) = docker_run_command.volumes {
+            command.args(container_volumes.into_iter().fold(vec![], |acc, v| {
+                [acc, vec!["--volume".to_string(), v]].concat()
+            }));
+        }
+
         command.arg(docker_run_command.image_name);
 
         if let Some(container_command) = docker_run_command.command {
@@ -315,6 +331,7 @@ mod tests {
         docker_run_command.expose_port(55555);
         docker_run_command.platform("linux/amd64");
         docker_run_command.remove(true);
+        docker_run_command.volumes(["./.test-cache:/cache"]);
 
         let command: Command = docker_run_command.clone().into();
         assert_eq!(
@@ -337,6 +354,8 @@ mod tests {
                 "127.0.0.1::12345",
                 "--publish",
                 "127.0.0.1::55555",
+                "--volume",
+                "./.test-cache:/cache",
                 "my-image",
                 "echo",
                 "hello",

libcnb-test/src/test_context.rs

@@ -112,6 +112,10 @@ impl<'a> TestContext<'a> {
             docker_run_command.expose_port(*port);
         });
 
+        if let Some(volume) = &config.volumes {
+            docker_run_command.volumes(volume);
+        }
+
         // We create the ContainerContext early to ensure the cleanup in ContainerContext::drop
         // is still performed even if the Docker command panics.
         let container_context = ContainerContext {